Abstract
ABSTRACT Soil attributes may affect the residual activity and impacts of herbicides on non-target organisms. This study aimed to evaluate the residual activity of the sulfentrazone herbicide and its impacts on microbiological parameters of Brazilian Savanna soils, as well as to identify soil attributes that can be used to predict the residual activity of the herbicide in these soils. The experimental design was completely randomized, in a 6 x 5 factorial scheme, with 4 replications, being 5 soil types (Rhodic Acrustox; Typic Quartzpsamment; Rhodic Haplustox; Typic Humaquepts; Fluventic Dystrustepts) and 6 periods (0, 15, 30, 45, 60 and 90 days after herbicide application - DAA). The residual activity of the sulfentrazone herbicide is dependent of the soil type, and the time that the herbicide can control at least 80 % of Urochloa decumbens plants ranges from 0 (Typic Humaquepts) to 38 days (Rhodic Haplustox). The bases saturation is the only soil attribute correlated with the herbicide efficacy over time, in the Brazilian Savanna soils, showing a moderate correlation up to 90 DAA. The pH, organic matter and clay content are not correlated with the herbicide efficacy over time in these soils. Sulfentrazone reduces the microorganisms activity from 45 to 90 DAA in all the studied soils. However, it does not affect the microbial biomass carbon.
Highlights
Brazil is currently the biggest pesticides consumer worldwide, with herbicides representing more than 50 % of the marketed products (Moraes 2019)
Regarding the GMd, no model fitted well to the DMR% in this soil (Table 4), and the DMR% was low even at 0 days after application (DAA), suggesting that the sulfentrazone had a lower efficacy in weed control in this soil (Figure 1), what was observed by Pacheco (2017) as well
The dry mass reduction percentage (DMR%) of Urochloa decumbens following the sulfentrazone application was greatly affected by the soil type and the period elapsed after the herbicide application (DAA) prior to sowing
Summary
Brazil is currently the biggest pesticides consumer worldwide, with herbicides representing more than 50 % of the marketed products (Moraes 2019). The Midwest region has the highest rate of pesticides use per area, with an average of 16.14 kg ha-1 (Bombardi 2017). The biome predominant in this region is the Brazilian Savanna, which is considered one of the 34 hotspots of biodiversity in the world (Myers et al 2000). Herbicides management strategies aiming to assure a high crop yield associated with low environmental impacts are very important to guarantee a sustainable agriculture in this region. There are many factors affecting the behavior of herbicides in agroecosystems, such as soil properties, environmental factors, herbicides physicochemical characteristics and management strategies adopted in the areas. The decision on which herbicide and dose to apply are reasoned in weed species and
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